The endothelium appears to play a central homeostatic role in maintaining normal vascular function and structure. Although the association between endothelial dysfunction and vascular disease is well established, its molecular basis and pathogenic significance remains poorly defined. Our central hypothesis poses that normal endothelial function is predicated upon a homeostatic balance between reactive nitrogen species such as nitric oxide (NO) and reactive oxygen species (ROS) such as superoxide anion. Furthermore, we postulate that the NO- ROS balance modulates several critical pathobiological processes involved in atherosclerotic coronary heart disease including : endothelial cell-leukocyte adhesion, vascular smooth muscle cell growth and migration, endothelial cell apoptosis, platelet aggregation, and decreased coronary blood flow. This project will test the postulate that the decline in NO bioactivity characteristic of endothelial dysfunction is a critical event in the pathogenesis of atherosclerotic coronary heart disease and that a gene therapy approach based upon restoring the normal NO-ROS homeostatic balance will be a novel and effective long- term treatment modality. We will focus on developing a strategy to "re- engineer" the endothelium to preserve the homeostatic NO-ROS balance by using three complementary approaches : 1) augment endothelial cell- nitric oxide synthase gene expression to override the increased catabolism of NO, 2) decrease oxidative stress-mediated catabolism of NO by augmenting the expression of superoxide dismutase (an endogenous anti-oxidant), and 3) prevent the emergence of the dysfunctional phenotype by inhibiting the cycle of oxidative stress-induced apoptosis and regeneration of dysfunctional cells by endothelial cell-targeted expression of anti-apoptotic genes. The success of this approach is predicated upon the development of stably integrating viral vectors for quiescent cells and vascular cell-specific targeting technologies under active investigation in this Gene Transfer Program. The initial phases of the project will utilize technologies of endothelial cell specification in genetically engineered mice to characterize the pathobiological significance of the NO-ROS balance in atherogenesis and cardiac ischemia-reperfusion injury. Based upon this characterization, we will utilize the novel viral vectors developed within the Program to further test this hypothesis in the context of animal models that simulate the treatment of human coronary artery disease.